1. Field of the Invention
The invention relates to an adjuvant for herbicidal compositions. This invention particularly relates to herbicidal compositions containing an adjuvant and an herbicide.
2. Background of the Art
Glyphosate (N-(phosphonomethyl)glycine in acid or salt form) is a known, effective herbicide. Glyphosate is the most widely used non-selective systemic herbicide that is used to control a broad spectrum of annual and perennial weeds. It works by inhibiting 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS), an enzyme of the aromatic acids biosynthetic pathway, thus preventing the synthesis of essential aromatic amino acids that are needed for protein biosynthesis.
The acid form of glyphosate is poorly soluble in water and for this reason glyphosate is typically commercialized as a salt that exhibits sufficiently high solubility in water to provide concentrated herbicidal formulations that are diluted by the end-user on field. For example, aqueous concentrated formulations are known of the isopropylamine salt (IPA), the monoethanolamine (MEA) salt and of the potassium salt of glyphosate.
Glyphosate is usually applied by the end user as a diluted spray aqueous solution. Diluted spray aqueous solutions of glyphosate typically include at least one surfactant. The presence of a surfactant is highly desirable since surfactants reduce the interface tension between the aqueous spray and the material (foliage) to be treated (i.e. they improve wetting), thus favoring the spreading of droplets on the treated surface, the penetration of the active ingredient into the materials and the overall bioefficacy of the solution.
Because of this favorable behavior, a great variety of surfactants have been described to act as “adjuvants” in glyphosate formulations. By way of example, U.S. Pat. No. 3,799,758, which is fully incorporated herein by reference, includes in the herbicidal formulation a surface-active adjuvant, comprising, among others: alkyl benzene sulfonates or alkyl naphthalene sulfonates, sulfated fatty alcohols, amines or acid amines derivatives, esters of sodium sulfosuccinate, sulfonated vegetable oils and ethoxylated alkyl amine, the latter being preferred in the majority of the commercial formulations due to its low cost and reasonable efficiency.
Alkyl amine ethoxylates, and in particular ethoxylated tallow amine, are most frequently used as adjuvants with pesticides, in particular as adjuvants for glyphosate. Various other alkyl amine based surfactants have been described to provide excellent bioefficacy to glyphosate.
Among surfactants which can be used for the afore mentioned purpose, aliphatic alkylpolyglycoside derivatives have also been known for a long time. These materials offer several advantages due to their low toxicity and good biodegradability, especially if compared with the ethoxylated fatty amines, which create concern for their aquatic toxicity.
WO 05/087785 discloses an improved process for making ethoxylates of alkyloligoglycosides and their use as adjuvants, in particular for glyphosate-based herbicides.
WO 2011/000880 describes stable aqueous herbicide concentrate composition containing potassium, ammonium or isopropylamine salts of glyphosate and anionic esters of alkyl polyglycosides containing a salified sulfonic acid group.
Lecithin based adjuvants for glyphosate are also known from U.S. Pat. No. 8,211,832. However, the use of common surfactants in glyphosate-based formulations has still some problems. When the surfactant is added to a concentrated aqueous glyphosate salt solution, before dilution, segregation of the components may occur, such phenomenon being known in the art as salting-out. In practice, the solution initially becomes turbid and this phenomenon is followed by the separation of the surfactant agent originally dissolved in water which floats on the surface, while the saline solution precipitates towards the bottom. For example, most classes of non-ionic surfactants, including polyethoxylated alcohol, are not compatible with high ionic strength solutions, such as concentrated aqueous solutions of glyphosate salts. Moreover, certain surfactants can interact with other ingredients during the production process and rising up the viscosity of the herbicidal aqueous formulation. If the viscosity is too high, handling/production process of the concentrated herbicide can be difficult.
The addition of a large amount of glycol or an alcohol, up to 30%, can be used to avoid such problems in concentrated solutions of glyphosate and surfactant that are commercialized for later dilution on the field, as described in U.S. Pat. No. 5,385,750, which reference is incorporated herein by reference. However, this means that the resulting availability of the surface-active agent is reduced in the same proportion, which causes a lower efficiency of the final product. Also, the presence of the alcohols creates considerable drawbacks: they give strong odors and cause a noticeable lowering of the emulsifying ability of the surfactants. To overcome these problems, adjuvant surfactants are often used in tank mix, i.e. they are added separately from glyphosate to the final diluted herbicidal solution; even in this case some problems may occur, such as crystallization of the agrochemically active ingredient that may give clogging of the sprayer nozzles, especially when glyphosate is used in combination with other herbicides.
It is therefore well known to those skilled in the art that it is difficult to find a suitable surfactant with good bioefficacy and enhancing property for glyphosate; however, finding a suitable surfactant with good compatibility in addition to good bioefficacy and enhancing property is even more difficult.
It has now been discovered that an ethoxylated phospholipid-enriched soybean oil which is obtained by ethoxylating a soybean oil comprising from 5% to 30% by weight of phospholipids is highly effective as adjuvant for herbicidal compositions. The ethoxylated phospholipid-enriched soybean oil is compatible with other actives and common additives and does not show the crystallization problems that rise with many other surfactants.